"Void the ability to use google voice nobody will buy obihai devices over devices from more reputable companies like linksys."
Linksys doesn't exist anymore. History lesson (as already referenced by Ostracus): The folks now at Obihai developed the Sipura products. <and there are some parallel details with regard to Cisco's ATA-186, that I can't recall>. Linksys bought Sipura, and didn't innovate; they just kept selling the same products with minor variations (PAP and SPA product lines). Then, Cisco made a feeble attempt to get into the consumer business by purchasing Linksys (not just the ATA business, but the whole company). They merged in their own technology and enterprise product lines, including SIP phones. After deciding to return to their core competency as an enterprise networking vendor, they recently sold the Linksys business to Belkin. The PAP and SPA ATA products haven't been manufactured, nor updated in several years -- they've been discontinued.
When it comes to the ATA market, the closest thing to a "latest generation successor to the PAP and SPA" products, are Obihai's line. Otherwise, you're talking about clones from Grandstream or a couple of other vendors that sell to the telco provider market.
Whether or not the ATA hardware market survives over the near-term future is related less to Google Voice/Chat/Hangouts than it is to the overall trends in consumer telephony: more mobile, less land line, and for land line, dominance by the broadband providers, with integrated modem/router/phone hardware boxes.