You can only keep players who want to stay. It’s either a new contract for the lad or we get the best deal possible and reinvest for the future. We need to get used to this, we will have player turnover until we establish ourselves as CL quality. Even then, you’re still in trouble when genuine European heavyweights want your players (think bale, Suarez and Coutinho)
It's a two-sided coin.
I understand your point and I even understand that there is some sense in him going due to his age (not that he's actually old) and that we'll probably not get a bigger offer.
But... how do we push on and press to become a CL club or a club challenging the top six on a consistent basis if, just as we look like we're on the verge of really pushing on, we keep selling our best players?
I have no doubt if he goes we'll get a replacement in but we'll be very lucky if they come close to doing the job Gueye does so well. There simply aren't many players out there like him, at the end of the day. So it will mean a change in style. Again, not a bad thing, but something that could well take time and just going off how long it took to adapt last season, if that something we can afford if we really want to catch the teams above us?
It's annoying to sell your best player when there's some utter dross left that needs to be moved on first.