It's only logical to delay re-signing until the very end of the season.
If your taking the 'delay' in re-signing as a sign they might leave then you're mistaken. This is basic negotiation 101 to boost value, especially in the case for elite players.
Yes this much is obvious if in fact GWS don't know his intentions to stay of go so yeah get your manager to play as much shadow games as he likes to milk them for every penny you want. However Isaac Cumming No 1 seems to think that the club already knows he's staying because it was already agreed to that they would let other players go. So really what purpose does holding out till the end of the season achieve if the club already know he's staying? I'll wait…