Hate to break the news here, but apparently there will be another MGS title. Sorry WK looks like he won't be making anything other than MGS for awhile.
Stealth Will Return in Next Metal Gear Solid Sequel

When asked about the stealth in rising, he responded that there'll be no stealth mechanics, but not to worry since the next MGS sequel will have stealth. Bummer MGS4 was such a great highnote to end the series on.