As it is it needs both. As a PVE only game it doesn't last more than a year. Plus there is not nearly enough PVE content DLC or not to keep it alive. Also as a PVP only game it would suffer tremendously. I mean D2 will have a lot stiffer shooter competition from BF1, Titanfall 2, Overwatch, MW Remastered (since Infinite Warfare will likely not do too well but it will have its population as well). And PVP as of now is not strong enough on its own to really compete with those games. As much as I hate to say it but Destiny really needs a PC population to drive and test changes mods and what not. But on other hand the PC population would rabidly pulverize this game over the past three years.