Though the pronunciation is different. When Gelecek is used in the meaning of "that which will come", such as in the sentence: "Yarın gelecek paketi odama bırak." (Leave the package that will arrive tomorrow, in my room), it's pronounced as: geLİcek.
Gelecek, in the meaning of "future", is pronounced as written: "ge-le-cek".
There was an ad a few years ago: "Gelecek de bir gün gelecek." (The future, too, will come one day.) Pronounced: "GeLEcek de bir gün geLİcek".
Definitely works in UK English. Do you really not ever say things like "In future, don't go out in winter without a coat!"?
Here you go, evidence BrE uses "in future": https://jakubmarian.com/in-the-future-vs-in-future-in-british-and-american-english/
True, but in that case (as your very interesting link explains) it means "from now on". It wouldn't work for this sentence" I want to be a lawyer in the future." Unless in some weird situation where the person had already qualified as a lawyer but had changed careers and was changing back, they could say "I want to be a lawyer in future".