That's the whole point though, we really just "don't know". Nothing is a sure bet. Items that are extremely valuable now, could be made completely obsolete with newer more powerful items released with 2.0. Mining could be changed to where your output score allows you to harvest more materials per swing allowing you to pull down 5 electrum ores per swing instead of 1. Speculation is fine, I personally agree with you on the shard piece, as currently shards/crystals are essentially worthless since recipes require so few and they drop in such large quantities.
But that's the counter point everyone keeps throwing at you with the redenomination arguments. You're very sure that items are going to sell for more relative value than they do currently. I'm really NOT so sure. Or I should say, I really have no idea which items those are going to be, and liquidating your gil supply into items is most likely foolish (provided that they actually make the means of obtaining gil 1/10th of what it is now). It's a guessing game at best and you shouldn't be betting on the redenomination of gil to all of a sudden make you rich from selling a stockpile of what items you perceive as holding value.
For all we know, melding rates could be drastically increased, making double/triple melded items extremely devalued, or materia might be allowed to be melded to already powerful dropped gear instead of just crafted items, or SE randomly decides to raise the level cap 5 levels. While item values might fluctuate, and you may "feel" as though you're losing 9/10ths of your gil, the reality is that gil is a MUCH safer bet on being financially secure going into 2.0. You seem sure, and I'll wish you luck that the items you are investing in retain their value, but the reality is you are playing a guessing game and just as easily could come out behind in this gamble.