Users will indeed be able to host their own servers/worlds in Xira Genesis. There will be by default a graphical server mode, or an option to run a command like dedicated server through the console option -dedx. The number of different worlds you can create will be based on the amount of available hard drive space on your machine. The size of each world (Number of maps, players, etc.) will be based on your available hard drive space and to some extent the amount of RAM you have.
There will be Graphical and Dedicated server options in Xira Genesis.
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