Boeing was granted a patent in March of this year for what appears similar to the Sonic Cruiser in structure but closer to the 737 in size.

Could this be the 797? Boeing Granted Bizarre Patent

Airplane configuration - Google Patents

Boeing also filed a patent on a guppy looking 737 size replacement the end of last year seen here:

Could this be Boeing's 797? - Seattle News - MyNorthwest.com

Both airplanes are twin isle.