The problem with the lack of support is much more subtle than just waiting for bug-fixes. The problems you are going to have will concern things like:

1) New wi-fi features - 802.11 was only released in 1997, many of the features of wi-fi that we now take for granted only became popular in the last few years. We have only recently got WPA in the Pronto, but we will now be stuck with what we currently have, and in a few years time that will be obsolete.
2) In my experience, the Pronto is incredibly flaky with certain types of wireless access point. If the ones that installers know are good stop being produced, we could find ourselves very stuck.
3) IR databases. As new AV equipment is released, we need to stay up to speed with the IR databases. I can easily envisage this becoming a major issue in a few years time.
4) Regardless of the intentions of Philips for maintaining spare parts, it is going to be increasingly more difficult and potentially more costly to replace things that go wrong. I recently had to replace my RFX9400 to keep my system running. In a few years time replacements like that may be difficult and costly, or even impossible.

I'm sure there are many other potential gotchas out there - these are just a few potential ones I've thought about in a few minutes. I could not in all honesty recommend someone go out and purchase a niche device such as this, which costs as much as it does, when the company that makes it has pulled the plug.

I actually sincerely hope that Philips manage to sell the Pronto line as a going concern. But I can also see the writing on the wall. The ubiquity of inexpensive high powered touch enabled devices like phones and tablets will probably change the way people do universal remotes within 5 years. At the moment, there are still some steps needed for the leap to happen, but I have little doubt that it will happen. If someone wants to spend development hours on coming up with a home solution for universal remotes, I would have to recommend looking to the future rather than back to the past.