A few notes...
First off - when I saw the shirt, I immediately thought "Oo, a shirt to say "I celebrated Disneyland's 50th at WDW!"
Not everyone can goto Disneyland. I celebrated the 50th of Disneyland and the idea of a theme park by going to WDW. I'm not the only one and i'm not dumb enough to think the shirt is saying "50 years of WDW."
I know not everyone is bright, and certainly not all Disney tourists, but i do find it insulting to say people would be so easily confused and misled. I figure if anything they'd simply not understand.. all the "100 YoM WDW" stuff they sold didn't make anyone think Epcot was 100 years old.
About attendance and proper investment...
DL reached capacity with days around 68,500 according to Al. Over at WDW's largest capacity park, Epcot, on NYE the last known "official" number placed it in excess of 90,000 at 8pm with an anticipated breach of 100,000.
WDW has expandable capacity - the likes of which Disneyland will never see. Even if this was some marketing person' askew way to bring people to WDW, they could atleast get into WDW whereas DL was running full and most folks don't want to goto DCA yet.