Just because there currently isn't a need to have hundreds of millions doesn't mean there won't be a need in the future. If I was one of those players who wanted all 7 relic weapons I'd be looking at spending at least 150 million on that process. All that would filter down to the less well off players. The housing in V2 will also be costly. What else will they add that is costly?
And anyway I made my fortune at a time when I was able to play all day every day. I have a job now and don't have time to make tonnes of gil like that. I am set for the future. Making gil as you need it isn't always the best solution. I like to plan ahead.
I don't think this is anything to worry about. If they redenominate then everyone stays the same. If they're simply lowering the max digit then sure some rich players will lose money, those currently not playing who don't hear about the change in time, but the rest of us will move gil between characters. That in effect makes me richer, because those people who get unlucky with it will be taking gil out the system.