Would you invest in a better PC for a next gen sims game?

Nope. I spent good money on a new rig for Sims 3 in 2012 and again for Civilization VI end of 2016. I think I'm set for a while. Have no problems playing Sims 4. I'm pretty sure my rig could handle a moderately higher grade of game -open neighborhoods and some control over colorization. But maybe not a fully open world and the entire CAST system. On the other hand I usually end up getting a new computer ever 4ish years or so anyways, so by the time the Sims 5 comes out assuming it's 2020/2021 I would be due for a new one.