Maybe it's not as simple as a software upgrade. Now I'm not as tech savvy as some of you might be, but doesn't "upgrade the platform" generally mean they are also switching out the hardware.
Quite possibly, although generally you wouldn't need any more downtime for a hardware upgrade. You'd stand them both up side by side, test the new system while the old is running and then do a "software" switchover (trying to be as non-technical as possible here).
In fact, not having new hardware and the old hardware not being capable of running both systems side-by-side is actually a possible reason for a
longer outage, but that (IME) is indicative of poor management/process.
I'm sure with something like a forum there would be data conversion issues and a period where you'd need to do a hard outage (or at least a read-only period), unless you have the big bucks for real-time data replication across systems running different hardware and software, but as Ulorian said, IME those outages are measured in hours (tops), not days. And I've been involved in some fairly tricky data conversions with financial and regulatory implications which I'm sure WotC don't have to worry about - worst case they'd lose a couple of forum posts here and there.
So yeah, while I'm not arrogant enough to think I know everything, my experience tells me that there's no good reason for an outage of this length, for the type of change/upgrade they're making.
Maybe next week WotC will announce that they're brought 4eBot online, integrating D&D Insider, spy satellites and robot drones and now anyone not playing 4e actually
can expect a call from the robot gaming police. But I seriously doubt it...
It's about time!
