Microsoft has started a new campaign offering people that get Windows 8 MCSA certified between February 15th and May 31st  to get a free Windows 10 exam (697) when it is released. For more information about the offer see: https://borntolearn.mslearn.net/b/weblog/archive/2015/02/19/how-to-get-a-windows-10-exam-for-free

Based on the comments on the born to learn website it seems that this offer does not extend to people that are Windows 8 MCSA certified before February 15th … but I might be wrong. An alternative is to try to get access to free Microsoft Beta Exams by signing up as a Subject Matter Expert (SME) as described here: https://blog.bjornhouben.com/2012/09/17/how-to-get-access-to-free-microsoft-beta-exams/