They're not going to implement Summoner. Yoshi-P doesn't like the idea of there being multiples of a primal and them not being extremely strong. Summoning will be a one-shot deal you earn every time you kill a primal, though to be honest, I don't like that idea either as it'll easily wreck PVE balance.

Necromancer is a class with lots of fun design space, however, it doesn't have a FFXI history, so it's less likely to be added. Also, these class request threads are way premature. You won't be seeing any classes that haven't already been announced/planned until after 2.0 if even then.