Splashtop is replacing SyncroLive as the primary remote desktop client. However, Syncro Live will still be there and you will still be able to use it; it is not going away. You are not forced to use Splashtop and if you would like to opt out, you can opt out. You should have received a popup alert when you login to your dashboard giving you the opportunity to opt out of it.
If missed the pop up and would like to opt out of the automatic application of Splashtop in your policies, you can do so by going into Admin > RMM Settings - Preferences > Splashtop Opt Out. Check the "Do not enable Splashtop on my policies at launch" box and click Save.
If you enable this checkbox anytime before Splashtop fully rolls out, it will prevent Splashtop from being enabled on any of your existing policies.