I’m not sure how many of you had the chance to take a look at the Message center in the Office 365 admin center last week , if you haven’t yet I would urge you all to take a look at this announcement which was made on Sep 25th about Microsoft removing the Visio web access/Visio web part and communicate the same to your end users/business .
Although ,it’s too early to talk about this change as the change will come into effect only from Sep 30,2018 onwards I think it would be worthwhile to start preparing ourselves for this change as the Visio web part has been one of the most heavily used web part by many SharePoint users for many years and with this change we should start thinking about at alternative now .
Vignesh's SharePoint Thoughts 
Someone might want to consider building a web part with draw.io, https://github.com/jgraph/drawio. It’s open source, so cannot be arbitrarily removed. Plus it imports .vsdx.
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