Given the past record of the big three US detector manufacturers, plus Whites' mis-steps with their most recent introductions (Treasuremaster and MX Sport), I wouldn't be holding my breath for the emergence of anything game-changing from the USA. Like them or not, Minelab is a company built on being technology game-changers and their recent successful introductions of the SDC and GPZ, maintain that tradition.
The primary focus of the US manufacturers has always been coin, jewellery and relic detecting, with gold prospecting as an ancillary function. Now that Jimmy 'Sierra' Normandi is out of the picture at Whites, I don't see them having the driving force to get back into the gold race in a meaningful way. The frustrating problems of the Treasuremaster and MX Sport - both straightforward, single frequency, VLF machines - highlight issues with software engineering and a deficient prototype testing program. Patents or not, I think it's questionable whether the company is capable of bringing to market a bulletproof detector based on a radically new PI/VLF concept.