I would like to understand the history of the modern expression “what say we” followed immediately by a verb phrase, used to make a suggestion and common in informal speech, as attested at Oxford Dictionaries
What say we take a break?
used in publication
“Gillette Raises Bar With Five Blade Razor”. What Say We Make It An Even Dozen.
and found in song lyrics
Baby, what say we stay together? (George Strait song “What Say”)
What say we go and crash your car? (Brand New song “Failure By Design”)
I stopped to notice that this expression is not, strictly speaking, grammatical and seems to be a contraction. I became curious what it might be a contraction of. There is the slightly longer “whaddya say we [suggestion (verb phrase)]” which is an informal version of “what do you say we”. This is still not, strictly speaking, grammatical. But it seems akin to “what say you to [suggestion (noun phrase)]”, such as the Shakespeare quotation offered in comment by AndrewLeach
What say you to a Neats foote?
which can equally be expressed as
What do (or would) you say to a Neats foote?
But I have no idea if it is reasonable to connect the dots.