Yes. With Unified Access Gateway support access to Horizon from the Internet, everything can be done with just TCP 443.

Other ports are optional. i.e.:

PCoIP on TCP/UDP 4172

Blast on TCP 8443 and UDP 8443

UDP Tunnel on UDP 443

It is normal to allow TCP port 80 as well as TCP port 443. This is just so that Horizon user's don't have to enter https:// http port 80 will redirect to https 443.