Considering the fact that at least DVD versions of both seasons of Sam & Max are widely available in retail stores, I would assume that also Tales DVD will be available in other stores too.
Then again I ordered both Sam & Max seasons DVD's directly from TTG, because thanks to the exchange rate between Euro and Dollar it was actually cheper to order games from California than from my home city (I don't go to gamestores these days, but I order everything to home, because for some odd reason on-line stores often have wider selection of adventure games, while stores on the mall mostly just have console games etc.).
And while some may hesitate to buy downloadable version I don't see any downsides in Tales deal which gives both direct download and DVD (you only have to pay the cost of shipping once it is available). I pre-ordered Tales and now I have already completed the game and I plan to replay it when I get my collector's DVD