There's no guarantee with any prospective coach and what it'll come down to is how quickly said head coach can implement his approach/style on the squad he inherits. Which will determine how quickly we can challenge for the league, and you also need a bit of luck.
Ten Hag's approach is well defined and it's a approach that has seen Ajax punch above their weight in the champions league playing a brand of football that is proactive but also well structured both on and off the ball. I'm not gonna go into too much detail but his approach to the game has caused many a problem to the biggest clubs in Europe for 'several years now'. And Ajax hadn't advanced past the group stage since 2005/06, until ten Hag arrived. It's not just in the Dutch league that he's impressed for Ajax and Utrecht but also the champions league, where he's imposed his play style on the best teams in Europe, coaching a brand of football that he's tweaked and adapted to the modern game, which has seen Ajax reach heights in Europe which they last saw in the mid 90s. He saw his 2019 team get dismantled and he's still helped rebuild the team in a short space of time and has Ajax again competing with the Europe's best. It's extremely ignorant for anyone to pass judgement on ten Hag by comparing him to de Boer or Koeman who both approached the game very differently. And if it was just just about the Dutch league I could understand, but his Champions league record with a team likes Ajax which is a club that has for a long long time not made a mark in Europe since the 90s, speaks volumes for a man who is displaying elite level tactical acumen.
And also more than half his current first 11, are players from a non Ajax back ground. Players like Tadic, Haller, Alvarez, Martinez, Antony, Pasveer and Berghuis, who all started against BvB. Only the two fullbacks (Blind and Mazraoui) and the young CB Timber are home grown from the team yesterday. So the assumption that the players come from a Ajax back ground, hence why it's easier to coach said style of play, doesn't stand up to scrutiny.
I think he's the stand out candidate and his approach to the game, along with his tactical acumen can bring about a major change which could potentially lead to the EPL title. And the reason I'm saying that is because he's adopted a way of playing the game, which is a proven winning formula, and he's fine tuned that formula for the modern game. So it all comes down to how quickly he would be able to get his ideas across imo. He's also had Coffee with Fergie in the past, so I presume it won't be difficult to touch base with him directly.