[Morsul the Dark]

I highly doubt it "at any rate he was too large and heavy for a hobbit" Tom Bombadil...

Bombadil could wear the ring without much trouble getting it on and he was bigger than the hobbits so therefore we can assume the ring grew enough for it to fit on his finger

Oh and another thing if it had grown too small for the big folk to wear why would gandalf have to worry about carrying it he would not be able to wear it