I travel I-75 and I-10 quite a bit both on business and pleasure and can relate that the norhbound RV parade has been going on for several weeks. I myself will be on the road back home next week to La. for the annual Easter crawfish boil and family visit so in a way I will be a short term migrator.
The small town where I reside in Central Florida has a number of RV parks that esentially cater to the "snowbirds". Do we have quite a number during the season, we sure do. Is traffic a little more congested, yes but not bad. Are stores a little more crowded with people with different accents, yea but I have not seen any locals go without because of "snowbirds". Now do the dollars they add to the economy help especially in a rural area without a large business base, absolutely. I know several small business's, oil change place, tire store, beauty salons and a few others that count on the winter season for a "good" year.
Can they survive without the winter visitors, sure they did before all the new parks opened up, however the extra income is welcomed by everyone so come on down you are welcome here.
Now as far as the economy of Florida collapsing without "snowbird", come on man get serious, there are many other thriving parts of the Florida economy that are not impacted at all by the tourist business.