All, I was asked Jim Woodhead and talked to Sage regarding Year End. Hope this helps. Version 4.4, 4.5 and 2013 you can print W-2 from MAS90. Version 2014 is untested. If you use Aatrix you only get a 4 part W-2 form, and you can either print them locally or let Aatrix send the forms to your employees, (my option). If you do processing in Aatrix you need to install 2014 IRD. If you use Aatrix then the 2015 TTU should not be installed or the 2014 should be reinstalled before processing. The files Aatrix uses in Sage have multiple years which I have not verified, Sage informed me we don't need to make a year end payroll backup company, though I still did to be sure.
Finally, I did install the 2015 TTU on a 4.4 system, not sure I will do the other clients I have on 4.4 this way, I may just change the Tax tables Manually.
Hope this helps