Is one-hour transit time enough in Hong Kong?

I am flying next year from Sydney to New York via Hong Kong and the transit time is only 55 minutes. Is that too short to make it onto the next flight or am i going to miss the flight? They are both with Cathay Pacific and i would be checking into Sydney all the way through.

It's definitely do-able as I find CX and HKG airport are quite efficient, but it can all depend if you depart SYD on-time or delayed. If the flight is missed due to the delay of you arriving into HKG and you've booked it all the way to New York on Cathay, they should put you on the next available flight.

CX run many sub one hour connections, so it must work most of the time. I've done 4 Perth to Tokyo trips and had one missed connection in Hong Kong.  CX put us in the airport Hyatt overnight and on the first flight in the morning. The other connections were easy.

I have travelled from Sydney to China about ten times over the last year with connection time of less than an hour in Hong Kong. On about half of those occasions we have left Sydney late and I have been worried about making my connection, but have always made it. My record (shortest) connection is 24 minutes from doors opening on my inbound flight to doors closing on my outgoing flight

If the connection is tight, they will have an efficient team right at the end of the aerobridge with flight number (and sometimes even names) to get you to the next aircraft as quick as possible. You get through the staff security line if it is crowded as well. HKG is one of the most efficient airports you can transit through. 

This will be a gamble. I transit thru HK on a reg basis and more often than not they have me on 60mins transfers. If the flight arrives close to on time you will probably make the flight although there may be a  chance your bags will not. If you more than 15-20 mins late your going to be bumped.

HKG is one of the better airports to connect through.

Towards the end of the flight into HKG, the IFE system on CX flights will show connecting gate information for CX flights (and limited known oneworld connections).
If the connection is tight, there will be CX staff at the arrivals gate with either express passes through security (and buggy/staff escort if needed) or new boarding passes for the rebooked flight.

Which flights are you booking? There are 4 SYD-HKG CX flights and 4 HKG-JFK CX flights (though one HKG-JFK transits via YVR) daily.

in my experience as long as you are on cathay it wont be a problem, if you are changing airlines you have no chance unless you only have carry on.

I've done it without drama. Wasn't much fun, mind you, because it's basically getting off one plane, getting through the transit channel, then getting onto another plane. There's zero lounge time if the gates are at opposite ends of the airport, and near-zero in most other circumstances. CX does very well at managing these tight connections, as Himeno has noted above. If there's no CX staff on hand, you want to check any slip they give you at check-in for your first flight which may have HKG transfer information – this will include a map showing the locations of the transit channels, because often there's a smaller one much closer to your arrivals gate than the main E/W transit portals, and that can be quite a time-saver. All that said: if you have a choice in your bookings I would definitely avoid a 1 hour transit, and especially if you have lounge access, shoot for 2-3 hours.

I should note that the connecting info on the IFE system will appear on the moving map rotation. (change to the map channel and the flight info will be in the rotation among the temp/time/speed/altitude info)

CX tends to give people with connections a connecting flight boarding pass holder. They'll slip the boarding pass for the 2nd flight and any lounge invites in the holder and normally attach the baggage claim check.
The holder has a map of HKG showing customs/immigration, connection screening checkpoints, airline transfer desk locations and the locations of CX lounges with selected gate numbers marked (just enough to get the idea where gates are).
This map is also in the CX inflight magazine.
Once you see the connecting gate info on the screen (it will also tell you which gate you should arrive at), look at the map and find the nearest checkpoint to the gate you're heading to.
Most people follow the signs and head to the main checkpoints or immigration. It might be quicker to head in the other direction, or past those larger signed checkpoints, to the smaller checkpoints if they are closer to your gate.
for example, you could arrive at gate 3 and be connecting to gate 31. It would be quicker to walk right past the transfer desks and main E1/E2 checkpoints and go through the T3 checkpoint. Less people on the arrivals level, a less busy checkpoint and avoids a lot of the traffic and shops upstairs on departures while getting you closer to your gate.

I flew LHR to AKL via HKG in Feb . Had a 55 minute connection from VS to ANZ , went perfectly. ANZ staff were waiting to show us to security  , even had 10 mins in the United lounge , all very impressive..

I had a 55 minute connection in HKG last year from London to Melbourne. I was all ready to rush but it was absolutely fine. Walked to transit gate, down to departures, I even had the chance to visit the lounge and have a very short shower and a few dumplings. If the connection time is really short, they'll have an agent to meet you at the gate and walk you through it.

All this assumes that your flight is on time, if it's late obviously there will be nothing they can do - you might want to check when the next Oneworld flight is as a fallback.

I've had a 55 minute connection from PEK-MEL on CX before ADL-MEL cancelled, but due to the Chinese ATC, our plane landed 2 hour late at HKG. CX even sent a representative to my arrival gate to handle issues (for being an oneworld Emerald member, maybe?), then they rebooked me on nonstop to MEL departing midnight. (original itineraries was PEK-HKG-ADL-MEL)

I got bumped last year with 60 mins between flights. Said my bags wouldn't make it. Only time I have been bumped. Emirates hold the plane to Perth a little to ensure no long waits. My original flight was late out of Manila...oldest creakiest 747 in the Fleet. Even the cabin staff winced at take off!