TLDR: Sounds Neat.  Do it if you can afford it.  Be aware of cost and risk factor of future support.

I have been mining off-and-on since 2014 and I remember quite well the FPGA interest back in 2014.  I'm sure there have been other FPGA efforts before 2014 but my point is to simply share my own opinion.

First, I'll just say this is probably a great opportunity for people who can afford this.  Not everyone will be on board to spend $5K to get a system running.  That's a rough estimate.. but $4K for the FPGA and then whatever else for ancillary equipment like mobo/ram/psu/etc.  

So people saying that this will cause the demise of GPU mining are being short sighted.  

Asides from being expensive, it is technically daunting.  We would be relying on a programmer for future firmware updates and from what I've seen the support is just not to the same scale as the existing support for other mining options.

So I'll just summarize by saying this sounds like an awesome opportunity for diversification of a mining portfolio if you have the money for that.  I imagine youtubers like VoskCoin would be jumping all over this.

TLDR: Sounds Neat.  Do it if you can afford it.  Be aware of cost and risk factor of future support.