Sources? I've always assumed that the bots are as good as the pros now even at high stakes. Haven't there been prized competitions where the bots beat the pros some years?
I can't give you a direct source; but there is very little public progress to bots in big bet (NL/PL) games past very simplistic, rule-based bots that may fair okay in nano-stakes games. Of course there an outside chance that powerful bots do exist and are being employed in live games, but there's been no academic work that claims much access.
However in limit games, where the game tree is finite and can be simplified, there's been great strides in poker AI. In heads up the level is expert-to-world class (see my other posts in this thread) and likely very strong in 6-max too. Academically the polaris team (uni of alberta) have published a great deal, and there are commercial/private bots that are considered very strong.
Perhaps I should I have clarified with No Limit. Yes heads up limit poker bots are pretty high standard. But No Limit (and 6+ players) is the real interesting game to solve.
