If I'm Washington I make that deal in a heartbeat and hope OKC doesn't think they need more coming back to them. No guarantee Beal (or anyone else that could be taken at #3) will be as good as Harden.
Another move by Washington to surround Wall with solid-citizen types. I like it for them a lot. I can see it for OKC financially but from a basketball standpoint, not so much. Beal's unproven and even though Harden wasn't particularly good in the finals, I'd keep him just because he puts pressure on the other team's SG.