p.o.m.frite
You won't be moved to ESA(IR) your remain entitled to ESA(CB) as long as your claim is continuous, you will receive an ESA(IR) top-up to your existing ESA(CB) payments.
If you are receiving any ESA(IR) then this will be transferred to UC when claimants are migrated, although this will be some time, it's not clear what will happen to ESA(CB) and whether this will be moved to New Style ESA which is the UC equivalent of ESA(CB).
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems