Great news. He clearly likes it here.
If he finishes strongly this season, gives us a 5th year and we go far in Europe and the domestic cups it's possible (would require 30-odd goals) he could get to 100 goals for the club. In 5 years, before the age of 25. That'd give him legend status in my book, regardless of silverware.
If he were to leave this summer, he's given us 4 superb years' service, become our record goalscorer in the league and Europe, shown absolute dedication and professionalism and has said he'd like to leave out the front door rather than the back, so if the offer's right and he wants to go, I hope we let him.