Will TESO will be moddable somehow in a limited form or extended like TES ?

no confirmation as of yet.

or well, we can make UI mods, like damage mods and raidframe mods etc, that is possible.

but no mods like we had in skyrim and oblivion (no info on those yet, perhaps for PvE only).

I believe the answer will be 'No' or 'Only the UI will be moddable'.

For an MMORPG maker to not embrace the three following communities:

RP

PvP

Mod/Add-on makers

Machinima

Is like the developer saying "I hate free money, publicity, and cost effective content!"

So they'd better have support for add-ons. But yes it won't be actual content modification. Maybe some limited control, like selling off useless items automatically or allowing you to lock certain "builds" and have the add-on swap to certain build automatically without having to drop and drop all those abilities.

Yes. LUA mods only though. forgive me another /thread.