Dan Aykroyd will be returning to the franchise once more in what would seem like a cameo. No word yet on if he'll be playing his original character or an entirely new character, Aykroyd returning should please some of the fans out there.
Earlier during the day, Aykroyd tweeted out saying “On GB set shooting my scene with funny beautiful Kristen Wiig Lady GB’S are adorable, hilarious and badass Exhilarating! #ghostbusters.” He has since deleted his tweet but Entertainment Weekly has confirmed his involvement.
Here is a link to the Entertainment Weekly article. http://www.ew.com/article/2015/07/14/ghostbusters-paul-feig-dan-aykroyd