It seems like a good idea to start by thinking about what's wrong with professions now. For starters, some of them are pretty awful to level. Leatherworking and Skinning are two that always seem to come up in discussions of the best and worst professions to level. And many of the crafting professions have material demands that so heavily outstrip supply that it's a hassle to get them done without raiding the auction house.
Catching up and staying ahead
The problem is less troublesome with professions that require gathering rather than crafting, such as Mining, Herbalism and Skinning, especially as the former two have a Pandaria catch-up system in place. Given how well those have worked, it's surprising that no such system has been implemented for Skinning, so it's likely to me that that's something coming with Warlords.
And Mists has seen other catch-up systems introduced for professions such as Cooking and Blacksmithing, so it seems likely that most professions will see a re-work with some kind of totally optional catch-up mechanic in the next expansion. It would also make sense with the introduction of level 90 boosts, that Blizzard doesn't want players to have to grind through over 600 levels of a profession to get that up to scratch. Of course it's possible that the boosted 90s will come with professions, but we don't know that yet. Based on the Scroll of Resurrection 90s, they won't.
Another major irritation for crafting professions that make anything other than enchants and gems is how the gear they put together becomes outmoded so quickly as the expansion progresses. While Mists has been better for this in some ways than Cata, crafted gear isn't even worth considering for many facets of the game. And with the cost of materials not always decreasing, particularly for Leatherworking, the value of the gear when sold can be less than the material cost. This is a tricky situation.
What's more, in Warlords, we've heard a great deal about how gems, enchants and similar will likely be in less demand than in the game as it stands. Something will have to fill the gap for these traditionally lucrative professions, so maybe they will join LW, BS and Tailoring in the gear crafting race. Blizzard have hinted at such changes already. Either way, the continued relevance of crafted gear is something that really ought to change.
Professions because you want to, not because you ought to
One thing I think could definitely change is profession bonuses. Like racials, there are good ones and bad ones. Nobody, in my opinion, should feel obliged to learn any particular profession because the perk it offers is superior to the other options for either PvP or PvE. Professions, to me at least, are things you learn because you like making money, like flying magic carpets, like having a Jeeves at your beck and call, or just like crafting things for yourself and others.
While I'm not saying profession perks should be removed altogether, I would at least like to see some balancing between the different perks so that none really stand out. There is reasonable equality at the moment, but I feel like more could be done. Blizzard is doing it for racials, as they've said, so why not professions? But that's my two cents. What do you think ought to happen to professions in Warlords of Draenor?