Selling character slots is an obvious 'replacement' for the loss of sub. (I don't mean 1:1 but it's an obvious cash shop item)
It's a little naive to expect 8 (for each profession) or more, where 5 is already a very decent amount (5 races, 5 personal stories).
At the time you'd want a 6th/7th/8th character slot, you probably already play GW2 for some time and thus the $/month really shouldn't be a problem imo. And for the 'casuals' and people who play GW2 + P2P, it's nice to have a cheap(er) game with 5 character slots. The B2P model is nice, but GW2 is not a charity. As long as they don't sell 'pay-to-win' or mandatory products in the CS, I'm happy.