Yeah it's been unfortunate that the electronic sensors have not been able to keep up with the optical readouts. Ion Torrent and Genapsys are barely used due to accuracy problems, but Oxford Nanopore's considerable logistical benefits of tolerating a wide range of input DNA concentration, quick time to data, low capital cost, and long reads has kept them alive. Maybe they will grow more with higher accuracy.
Illumina's patents ending recently has prompted a few new startups beyond 454.bio, including Element and Singluar, but with the stiff headwinds of FDA regulatory uncertainty and the long capital life of existing sequencers, it's hard for them to make progress even when they are far cheaper than Illumina. And then we have Ultima and MGI. The me of 10 years ago would not believe both 1) how many strong entrants we have to DNA sequencers these days, and 2) how much Illumina continues to dominate in sequencing. At some point us biologists only have ourselves to blame for our purchasing decisions and their consequences.