They'll end up with Bilic or Bielsa in my opinion.
De Boer seems to be linked with clubs like us on a consistent basis, so not sure why he'd go to West Ham - they've got potential but his stock is at his highest now, he may not get another opportunity like this. Same goes for Klopp and Unai Emery. Klopp is taking a sabbatical and Emery will either stay put or end up at AC Milan (not exactly a good move but.... 'istree as our Scouse friends would say).
As for Bilic and Bielsa they've both gone down in stock somewhat recently. Bilic hasn't really impressed since his Croatia job, with his stints in Russia (was it Lokomotiv?) and at Besiktas but seems to constantly be linked with Premier League; plus he's a former West Ham player so I could see that. Again Bielsa although he started really well at Marseille, as usual his squad has died and they missed out on the Champions League when they were challenging for the league around Christmas - It'd be interesting to see what he'd do at West Ham, as I imagine there's some players in that squad he'd really like.
But good on West Ham, to be big you've got to aim big. It'll certainly be interesting to keep an eye on them next season that's for sure.