Regarding your EXP question:

Yoshi during interviews have stated that the Main Story will have the EXP rewards implemented/adjusted for higher yields. This to me infers that you WILL be able to level up to 60 before you even step into Heavensward. If there IS a Level Cap break, I'm sure it will be tied to the Job Quest and not Ishgard, considering it wouldn't make sense to "increase your level" using the MSQ.
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I for one have 16 leves completed, 6 Beast Tribe Quests completed, and a couple 4X quests completed in my Quest Log to turn in for instant Level 51 when the expansion hits. However, if it doesn't work for whatever reason, I'll just discard the quests. No harm done preparing.