Do you know the new domain's history? It coulde be a disaster if you move your old domain to a new domain that has a bad history or a pre-exisiting Google penalty. Consider that a sites age definitely indirectly impacts rankings, so assuming your new domain is clear and have no penalty, you still can loose some rankings.
Read more on this:
Forbes Welcome
Changing Your Domain Name Without Losing Your Rankings
https://moz.com/blog/seo-guide-how-t...y-move-domains