Well tbf I didn't actually say that I think they'll finish 5th next year. What I meant but didn't make explicit is that within a reasonable time frame they're easily capable of finishing 5th. But if I was pushed then yes I ALSO think it's entirely possible for them to finish 5th next year just like they did last year.
You ask who they might replace in a year and one month without seeming to realise that the top 5 is in flux OVER THE NEXT MONTH, let alone over the next 13 months. There is no established top 5 to break into! Beyond the top 3 and bottom 3 the league is vey competitive and fluid.
But to spell it out: I could see Spurs finishing above any of Villa, Newcastle, Chelsea, and Forest.