I suppose in some cases, you might also use “níl mé cinnte / níl a fhios agam … (an dtiocfaidh sé srl.)”.
If “I wonder…” is meant as a non-commital reply to a statement you don’t agree with, e.g. “Soon people will fly to Mars”, you might perhaps say something like “Ab ea?”, “Ab é an chaoi?”, “I ndáiríre?”?
