I have a first generation IPad which is no longer supported for updates, will I be able to print on a wifi printer?

You print using airprint to an airprint enabled printer. (To the best of my knowledge iOS 5 supports that, but I'm afraid I can't really recall if it came with 5 or 6)

Or many printers have apps or workaround you can use (some have partnered with google docs to have various sorts of work arounds such as e-mailing your document to a hardwired local coputer, or in some cases, the printer itself)

There are also printing apps that may be compatible back to iOS5 and you can use those to print.