Joining NATO

Does anybody think that east european nations wishing to join NATO should Scrap their obsolete combat types such as the Mig-21 ( I don”t care what upgrade its had its still obsolete!) or Su-25 in preperation for new western types.
The period their airforces spent without combat types could be spent training aircrew overseas, upgrading airfields,radars & communications to Nato standard therefore allowing the regular deployment of NATO aircraft to unfamiliar airfields( training both foreign aircrew/ground crew and home ground crew / airtraffic controllers etc ) to provide National air defence( also allowing home air staff to task aircraft )
The regular deployments would also not only help interoperability but also add an insight into what aircraft would be best for them.:D