1.I think the lower ranked members is never going to rank up to legendary.
In more than 2 years, if you actually contribute, you should have no problem reaching 1000 posts that have been given 1 merit, 500 posts that have been given 2 merits, etc.
We don´t know if that is true because we don´t know how scarce is merit going to be. For example, in a extreme case, if only 1000 merits are created by the sources in a year, getting 500 will be nearly impossible.