The other factors are indeed relevant.
For me though the most relevant is do KLM have a contract with MME until a set point in time and when is this? If the answer is no, then KLM will leave when they can yield a better return from these aircraft elsewhere. What is worrying is that with such an obvious and clear decline, the number of alternative uses will increase each and every month.
On the future of the F70, we know they're not the most reliable and 7 will leave the fleet shortly. The remaining 19 will stay for a handful of more years until they decide on a replacement.
Sadly, if the current trends continue, we won't be around to worry about whether MME can sustain E190 operations or not.
Bigger aircraft at NCL with the odd extra frequency may not be a bad idea....