[William Cloud Hicklin]

You know, it's just possible to make a case that in the very earliest stages of writing The Hobbit, or at least making the original version of the Wilderland Map,Tolkien had Beleriand in mind. The Misty Mountains were the Ered Wethrin (lit. "Mountains of Mist"), the Great River was Sirion (lit. "THE River"), and Mirkwood was Taur-nu-Fuin (lit. "Forest of Dark Shadow"), complete with Sauron holing up there- and Tolkien even recycled the painting of Turin and Gwindor there and titled it Mirkwood! The Withered Heath would correspond with Anfauglith (which was literally "withered" from Ard-galen, thanks to dragonfire). The "Edge of the Wild" meant leaving the relative safety of Hithlum behind.

And there's I think just a hint of an intermediate stage where the Misty Mountains were the Blue Mountains, and crossing them meant leaving Beleriand for Terra Incognita.

Of course, that idea disappeared very, very early since already by the troll chapter Gandalf says Gondolin was sacked "many ages ago."

But the more likely explanation is simply that Tolkien was just recycling bits and pieces of Silmarillion ideas without any conscious intent that Mr Baggins existed in the same universe, any more than Farmer Giles or Mr. Bliss did: Thranduil's halls recall Menegroth, but in pictures were copied from Nargothrond; the Gwindor/Mirkwood painting was just economical repurposing, (it was recycled yet again as Fangorn); Smaug on his underground hoard reflects Glaurung in Nargothrond (itself echoing Beowulf and the Volsung legend); the Great Eagles and Elrond were straight-up lifts.