can my opponent take the 8th point if i end the card in the deck ?

Yes — a point your opponent gains from your Burn Out can be their 8th point and win them the game.

Only points scored via Conquer or Hold carry the Final Point restriction; points from other sources like Burn Out have no such limit, so the win happens immediately during the Burn Out sequence rather than waiting for a Cleanup (Rule 431.3.c; FAQ #1303). Note also that you don't actually need to "end" the deck deliberately — if your deck and trash are both empty and you're instructed to draw, Burn Out repeats, giving an opponent 1 point per iteration until someone passes the Victory Score (Rule 431.3).

If instead the 8th point would come from your opponent Conquering, they'd need to have scored every other battlefield that turn — otherwise they draw a card instead and no one wins.