In general service providers don't provide up to date versions of appium (such as the master branch) because it takes resources that they'd rather spend elsewhere. With that said, Sauce supports all appium releases (including appium 1.3.4 which is the current released version). You request the version via a desired capability.
caps['appiumVersion'] = "1.3.4"
https://saucelabs.com/platforms/appium