If you mean is there a mama Siri to manage all the little Siris, the smart home and the smart car, then the answer is no. However, there is a huge amount of research going into Multi-Agent Systems. There are also a number of macro type programs, that allow you to control other programs, such as AutoHotkey [1], AutoIt [2], Sikuli [3], Selenium [4], Ubot Studio [5], and WinAutomation [6], which could potentially be used for this purpose. And on the dark side, classic Botnets could be described as a form of “Meta-Assistant bots”.
[1] 100 Best AutoHotkey Videos – Meta-Guide.com
[2] 100 Best AutoIt Tutorial Videos – Meta-Guide.com
[3] 100 Best Sikuli Videos – Meta-Guide.com
[4] Best Selenium Videos – Meta-Guide.com
[5] Best Ubot Studio Videos – Meta-Guide.com
[6] Best WinAutomation Videos – Meta-Guide.com