If you are P3D believer and have iron hands, you won't be bothered by GHOST3D being Tron exclusive dapp. First of all, Team JUST will get a lot of exposure (by a lot I mean A LOT) due to Justin Sun shilling it. This indirectly benefits P3D already.
Do you want to benefit from GHOST 3D as P3D holder? Here's my strategy how to do this.
I assume you hold some ETH on the side - that is good idea as Team JUST releases external dapps from time to time. As GHOST3D will be released around Christmas you should convert some of your ETH into TRX. Then you can directly benefit from the new Team JUST's Tron dapp.
It is unknown how the GHOST3D is going to work. Most likely it will not be P3D clone on Tron. I assume that being early in the game grants you benefits, so if you got early (you had TRX ready to invest at launch), you probably made profit. Now I would leave some TRX in case there are more Tron dapps being made by Team JUST, but the rest should be exchanged back to ETHEREUM. Now you can transform Ethereum profit to P3D.
That's how you benefit from GHOST 3D as P3D holder.