Yes and No...
WikiTree no longer offers an automatic 'import' or 'upload' of information; however, you can upload a GEDCOM file and view GEDCOMpare results.
Since WikiTree is a collaborative site, some of the ancestors in your tree may already be included here in the WikiTree database. The idea is that your GEDCOM information is compared to existing information, and suggested matches are given for each person in your report. This way, any data you may have can be added to an existing profile, without creating a duplicate record.
After all of the possible matches have been cleared out (either confirmed or rejected), you will unlock the ability to 'add' new profiles of persons that are not yet existing in the WikiTree database. This 'add' feature is not the same as just taking your information from your GEDCOM and slapping it into a new profile, but instead takes a few key elements that can be translated from the GEDCOM (First and Last Names, Dates, etc.) and then allows you to enter in the biography and sources manually.
I would suggest starting with a small GEDCOM file, that way you can see how the GEDCOMPARE works, and it will also give you an idea on the amount of information that WikiTree may already have on your family.
For more information on the GEDCOMpare and how it works, see: https://www.wikitree.com/wiki/Help:GEDCOMpare
For more information on how to obtain a GEDCOM file from other software/sites, see: https://www.wikitree.com/wiki/Help:Exporting_a_GEDCOM