It won't happen unless Lin goes which also won't happen. I don't see Lin playing backup PG at this point and neither can be switched to the 2.
Also for a high assist PG Melo isn't ideal to work with. Melo makes more bad shots off dribble than open catch and shoot ones honestly, and we all know Melo likes to dominate the ball and isolate. If we didn't have Lin he would sign here for sure I think tho