first... my disclaimer. anything i say in this post has no guarantee to it, and has not necessarily been heard from any reliable, or in-control-of-the-game source. it is solely based on heresay, guesswork, and observation.
i will be fighting north to the new 500k block as well, for the following reasons.
there's not much left in the north city to clear. and even if there is a building hiding, we have no indication if/where it might be (admitedly, our last building was unexpected, based on comparisons to the hung game).
i don't think monstalogy is a valid reason to open up new squares. i remember the days back when only 2 or 3 squares were available to populate. we made a conscious effort to try and populate every possibly monster on them. now, i would prefer to do the same to every block (with the exception of the 4 or so 'preserved' squares), before we open more.
the land bridge is a potential can of worms. i remember hearing (again, based on memory... so this may not be all that correct) that when the north and south were connected in the hung game, the game was introduced to "trolls". it might seem like a welcome upgrade, IF we were to get it, but from what i remember, it was described as quite a pain, and a hinderance to things people were trying to accomplish on TA (i would compare it to the time we opened the north port block, and dropped items from TA monsters switched from only non-marketable items to marketable only... which was a good and a bad thing at the same time).
also, i highly doubth FOD would put us on this wild goose chase without there being something hidden. i do guess they've probably added extra monsters to prolong the time til we get there, which is unfortunate. but it seems, with squares getting "fuller" of monsters, there could be something important behind the walls of monsters. for all i know, it might be the beginning of "trolls" (mentioned above), or it could be some new, important building(s)... possibly the altar and table rumoured to be in the hung game which could potentially be very useful, but which were not in our game, on the same square as they were in the hungarian game. anyway, if there are "large" buildings to build, i would rather we open them up asap, so that we stop wasting nubs by selling them. clearing 3 or 5 other blocks before we push through this 500k would mean a ton more sold nubs, no longer available to build any large building which might be back here.
and last of all, with two squares (not even beside each other), at 500k, there's likely an even larger square touching those two we can't see yet (600k? 1000000?) which would be the eventual target square. at the rate we cleared 300k, the next square will take at least 3 months, and a 1 mil square would take 6 months. and those are probably bare minimums. so the longer we delay getting to these squares, the longer til we find what's behind them.
and so... i fight north into 500000 monsters!
--jason