Returning player, lvl 30...should I wait for story double xp?

[ekatss]

I'll be honest with you, going from level 30 to 2.55 content takes a bit of time, but it is doable if you have some free time on your hands. Although after the patch hits, you'll have much less people doing the story quests than now, so expect longer queues for story related stuff after patch hits.

[Garlyle]

so expect longer queues for story related stuff after patch hits.

Not quite true. For one, players doing dungeons for the first time will have priority queueing. Second, everyone has levelling to do - either in new content or old content. Low Level Roulette is going to see an absolutely massive surge in active players, of all roles.

If you want to hold off a couple days, feel free! Take the opportunity to level some off-classes and try out other things, and then reap the benefits when all the new benefits for "new" players kick in!