I am buying domain for saas app. Does buying .com or .co or .io or .so impact SEO? As SEO is long term game will my current decision have any impact in future?

.com if possible http://www.paulgraham.com/name.html

While .com is more credible domain over others e.g. .net etc..but technically Google won't discriminate non .com in rankings as long as you are fulfilling user's intent.

Ok thanks