Regarding the cost of skills...

well Skills start costing a lot more after you buy 40 or so and it's not that big of a deal but, when the expansion comes, will the cost just keep going up or will the costs reset?

I doubt that you will see additional skills for exisiting professions... with the possible exception of a few elites. Adding lots of skills will just skew balance for several weeks/months until the tweaks are made. Elites can be added easier since you can only take one.

Instead, I would expect that you will see several new professions and/or races.

Hmm, that sounds reasonable, they would have to increase the amount of characters we could have as well if they did that and that would be nice.