Senior management changes could be afoot at Twitter. It is reported to be in talks with co-founder, Jack Dorsey (he who sent the first public tweet five years ago this week) about making a full-time return to the company in a senior role.

According to reports this move could see Dorsey return either as chief product officer or even possibly CEO.

If Dorsey does take on the CEO position that would mean changes for current CEO Dick Costolo. Costolo took on the job in October when founder Evan Williams stepped back to focus on strategy and development.

Business Insider suggests that whichever scenario plays out Costolo will stay with Twitter as he “is valued for his monetization expertise”. Along with product development, monetization is a clear priority for Twitter in 2011. Last year Costolo said that Twitter was about to start taking millions in ad revenue.

“In November, we reported that Jack Dorsey was, one day a week, working at Twitter again. This new position is said to be closer to a day-to-day job supervising product development at Twitter. It’s possible, however, that Dorsey will end up merely expanding his current consulting role,” reports Business Insider.

Dorsey is the one who came up with the idea for Twitter working with Florian Webber while at Odeo. And his three guiding principles are shared by the whole company and through its culture.

“We have three principles we build the company on: Simplicity, constraint, and craftsmanship, and we’re allowing those principles to guide whatever we do,” he said speaking in 2008.

When Twitter first launched Dorsey CEO before the role was taken up by Williams in 2008.

Dorsey went on to found mobile payments company Square where he is CEO.

Last week it was reported that another Twitter founder, this time Biz Stone, was taking up an advisory at AOL.