True, I can't really argue with the logic implied here, but finding water elsewhere might still not be a guarantee for life. Again, how inevitable is the development of life when for example water exists on a planet?

We do know that water must have been very important for life (on earth) to develop, so yeah finding water gives a planet a higher score on the likeliness-scale of finding life for sure.

Then again Mars has polar icecaps and frozen ice layers under it's surface, yet micro-organisms or fossils haven't been found yet. I'm not saying they won't find them there, but it would have quite some implications on how we will think about these questions.

Obviously it takes a huge amount of time and effort to research an entire planet like Mars, but it wouldn't surprise me either way. As in, yes the conditions seem to be good (although needless to say (at the moment) Mars is a much more hostile planet towards life than our earth), yet possibility doesn't imply an inevitability.