I mean, i like to see that blizzard replaces the cards that rotates out, but at this point i don't think people will run desperatly to buy classic packs just for those cards. And letting people craft them cheaper, (Legenday 400, Epic, 100, Rare 20, and common 5), maybe could help them to see some testing at least.
Edit, the poll should say "Yes, the first 2 WEEKS", not weels, my bad
I've fixed the spellings for you. And cast my vote. :-)
I quite like the idea of new cards having a "grace" period, expecially for sets like Classic where you may (like me) already have the whole set but to just try and unlock a couple of extra specific cards, getting whole packs would be a pain.
That said, it does make Tavern Brawl rewards a little more useful.
Their strategy for releasing new cards between expansions comes in two flavors:
Legendary cards, which are given away for free to everyone (usually in a golden version)
Additions to the Basic and Classic sets
In case 1, it is free, so you don't need to worry about it.
In case 2, only the Classic legendaries would even be worth having. For the Common through Epic cards, most people aren't even going to want them because they are going to be weak cards. For the legendaries, it gives you a good reason to care about opening Classic packs.
If you don't have all the Classic legendaries yet, wanting the new ones isn't any more of a burden on the player than wanting the existing ones you don't have.