I don't think you will be able to get a solid answer that's guaranteed to work, only wild guesses. Keep that in mind when making your decision.

No one knows how much they will change astros. They might tweak mana management, spell potencies, cooldowns, heck maybe even alter some of the mechanics. It is also possible that they won't change anything major and only adjust certain values (judging from previous promises).

Buy the essential items for your SCH to keep up with your static's progression and hold on to your remaining Esos / savage pages until 3.1. They will also introduce the new 24-man raid in 3.1, so even if you are behind in gearing your AST, you'll most likely be able to get it up to speed.