I would love a bargain extension now somewhere in the neighborhood of $40/4yrs, but I understand that is unlikely from Smart's point of view.
I am not sure what he is likely to make on the open market. He's a young player on a rookie deal and it doesn't seem like the demand for him has been all that high. Fewer teams will have money next year and there are some marquee free agents available (as well as non-marquee ones like AB) who will be ahead of Smart for the big contracts.
If this salary cap spike has taught us anything, it's that the big name free agents are really going to cash in, while the middle class may be left out in the cold - it wasn't as apparent last year, but it showed more this year (is Aron Baynes really that much less valuable than Smart?). This especially holds true with the increase $$ amount in rookie contracts, as well.
I LOVE Smart and hope he will be with the Cs for a long time...and I think he will.