Mfj shutting down.. how will this affect other aspects of the hobby?  

I Recommend, Echo Link. Young people, going to uses the computer as ham radio.

I have one of their tuners here that I love and hopefully someone will step up to fill the void

It's too bad, since it's always helpful to have competition and options. Fingers crossed this creates a opportunity for someone/something new.

They are only shutting down the manufacturing in Mississippi. Some of the foreign production is still going

Definitely a shame to lose MFJ. I have some of their stuff and have always been happy with it. 73's from KA9PHI

Free market capitalism, a vacuum will be initially created, then someone will come in and produce a product to fill the gap if it makes financial scence.