Now, I'm sure I may be in the minority here, but let's think this through...
Personally, I've thought about integrating M:tG cards into my own homebrew. I find the monsters, spells, and artifacts are much more interesting than their current core counterparts. Frankly, I'm bored to tears of core
anything, and believe that a M:tG style campaign world et al might be interesting.
Keep this in mind as well: D&D Minis was 'integrated' into core. You can play both separately; many of the rules for 3.5 combat and Minis combat cross over, and the boys at WotC even give you D&D translations to/from the Mini rules.
I think having all the D&D spells on pretty spell cards with pictures, flavour text and effects would be wonderful.
I remember that TSR tried this a long time ago with spell decks and magic item decks, but these were more like index cards than playing cards. Yech!
Such a thing might better suit newer players, as veterans already know what most magic items and spells do. But, if WotC goes 100% with the concept, players and DMs might consider picking up a deck or two, if only so they have a quick reference to said items.
And of course, encouraging players and DMs alike to purcase new and exciting cards to add to their repertoire... well, WotC is a business, after all.
