For lvl 60 chars, outlands will be pvp anyway, so there won't be much difference in lvl'ing up in pve or pvp servers anymore. So maybe they might open pve>pvp for lvl 60 chars, are there any hints/posts about that anywhere?

No. PVE servers do not auto-flag everyone in Outland, they simply have overworld PVP objectives like the Plaguelands do. PVE -> PVP transfers aren't going to happen anytime soon if ever.