Yes, SPECULATED is a Scrabble word!

Letter values in Scrabble US: S 1, P 3, E 1, C 3, U 1, L 1, A 1, T 1, E 1, D 2.

Is it a valid word?

SPECULATED is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

to believe especially on uncertain or tentative grounds
talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion
reflect deeply on a subject
invest at a risk

Also: chew over, think over, mull over.

Not playable in Scrabble US: HYPOTHESISE.