Wiktionary
contraction (context nonstandard English) Shortened form of ''what will'' and ''what shall''
Usage examples of "what'll".
What'll prob ably happen is we'll hit the water and there won't be any kind of biochemical interaction.
And through the interstices of this clamoring Bibbs could hear the continual booming of his father's heavy voice, and once he caught the sentence, "Yes, young lady, that's just what did it for me, and that's just what'll do it for my boys--they got to make two blades o' grass grow where one grew before!
I know what I know, and I know we had it all arranged, and you should stick up for your holders, not these weyrfolk and all their queer customs and doings, and I dunno what'll happen to my daughter.
If these things start crowding out the stuff that used to grow here, what'll the bugs and the kangaroo rats and the jackrabbits eat?
There's another outcropping of high quartz concentration over in what'll be Griffith Park, and that place has some bizarre happenings of its own, but this place is the mother lode.