No, there was never any upgrade - the forum was deliberately closed by Dan in late 2010 / early 2011, when he stepped down from the role of Admin, i've no idea who put the upgrade message up I suspect it was just left from the last time the forum was closed and nobody had any reason to change it. Since I was originally going to close it before I left, I had absolutely no problem with Dan's final decision as Admin as, in my opinion, it was always going to be a stay of execution and keeping it going had only delayed the inevitable in the first place.
I don't see the forum as having closed its doors as you can still post. I think it's more that it was 'upgrade in progress' for ages and people were driven away.
I re-opened it a year or two later (or rather I re-enabled it in the same Status and Member permissions as it was left by Dan), largely out of respect for those who had contributed so much information in the early days, as it was still a valuable archive of online information. I haven't seen nor had any contact with either Paul or Dan for several years, but I'm happy to say that i'm still in touch with several of the first members to register here and the original moderating team, although the forum is never discussed.
Like I say, the forum was brought back in exactly the same state as it was left when it was closed and I see that a number of members had voluntarily left the forum or had requested their accounts to be de-activated in the months prior to Dan closing its doors, so I suspect only a minority of registered active members can still post and I see that a handful of members did post for a while in 2012 - 2014 after it was resurrected but the forum wasn't actively being run by anybody during that period, it was always a "ghost ship" and I see that most of those posts during that period were in relation to that!. There are also over 4000 pending new registrations in the validation queue dating back to about 2012, so new members can't post either, and of course there is nobody here to approve them, so with no new input you aren't ever going to replace the natural turnover of members.
I was approached a few years ago by an individual who wanted to open its doors and give it his best shot again, reluctantly I agreed but I see nothing came of it and it doesn't appear much attempt was made and in all honesty I think that is for the best. Some things are best left as they are.