I wrote a program to convert Suunto dive logs. See more details in this post.
I'm betting you can convert your dive from another computer to a FIT file using the Fit File Repair Tool. I'd like to test this..........can anyone can give me a sample of a FIT file from a dive?
I do not understand why this keeps coming up. Garmin Connect is very good for what it was designed for, a central site to display all activities. This means that while it does display some quite well, most adequately, and some poorly, it will probably never be the best option for all users and activities. This is why Strava is very popular for people who run/hike/swim/cycle as it takes these activities directly from Connect and displays them in a more user-friendly fashion. Strava also takes Scuba activities, but really has no idea how to display them.
Personally I would not recommend Connect as an online dive log for all your dives. Take a look at online dive logs like Sub-Surface or Divinglog. They offer a much more complete online dive log and can accept imports from other programs, Sub-Surface also does have a direct import from the Descent though I have only played with it as I use a Shearwater Perdix as my primary dive computer.
I really do not expect Garmin to make any major updates to add dive log functionality that is not already in Connect. I also would be concerned about getting your dive log out of Connect down the road when/if you move to a different dive computer. I personally use Sub-Surface, and while the UI can be a little awkward at times, I highly recommend the program if you want to have an online dive log.
I wrote a program to convert Suunto dive logs. See more details in this post.