6.0 Mystery Zone Speculation

[Seraphor]

Silvertear Lake is likely going to be the entrance to Pandemonium and be the equivalent of a post-final boss bonus dungeon.

You say 'likely' but there's literally nothing to connect those things at all. Nothing more than a link to Hydaelyn or the planets core at any rate.
It's all baseless speculation.

We were however told that Pandaemonium takes place in an entire new location. While gaining access to this new location via Silvertear is obviously still an option, this 'new location' was made to sound important or unusual.
Given that Pandemonium is from hell, I'd wager it's location is in Tartarus.

[Ultimatecalibur]

You say 'likely' but there's literally nothing to connect those things at all. Nothing more than a link to Hydaelyn or the planets core at any rate.
It's all baseless speculation.

I wouldn't say baseless. Pandemonium/Pandaemonium is three things: "wild and noisy disorder or confusion; uproar," "the capital of Hell in Milton's Paradise Lost" and "the infernal regions : Hell." Since the concept of the "Noise from the Star" that destroyed Amourot was introduced in 5.0 people have been speculating about it. The Japanese also love wordplay and Pandaemonium being both a word for "Noise" and the capital of Hell used as FFII's final dungeon makes for some serious wordplay with a reference on top. The pathway to Pandaemonium being sealed under a lake would be similar to the location of the Jade Passage in FFII.

As for the new "completely original" non-referential Alliance Raid series and the long running mystery related to it we likely will not find anything out about it until May.