if i have astral heron on bf and i play a card at it, and move him to base and go to another bf is the next card 2/2 reduced still?

Yes. Once the trigger fires — you played your first card while the Heron was at a battlefield — the discount is locked in and doesn't care where the Heron goes afterward.

The "if I'm at a battlefield" check happens when the trigger condition is evaluated, not when the discount applies (Rule 383.2.c). Moving him to base, another battlefield, or even having him killed in reaction changes nothing — the discount is a pending effect independent of the Heron (FAQ #11792, #11729).

One catch: the errata'd text limits it to "the next card you play this turn," so if you move the Heron and then end your turn without playing that next card, the discount expires (Rule 317.2.c).