Microsoft future plans for the old-fashioned "List Threshold" limit.

One of the main reasons some customers got afraid of using sharepoint online is the list threshold limit of 5,000, which unlike the on-premises can not be expanded. now i know that there are workarounds for this by using indexing & folders. but the problem that some columns can not be indexed such as managed metadata columns which allow multiple selection. For example i have a case where the customer is using sharepoint on-premises 2013. and they have an enterprise wiki site collection. the Enterprise wiki site collection have these main components:-

1. 6 managed metadata columns, and these managed metadata columns allow multiple selections.

2. the customer enabled the metadata navigation and filtering for the wiki pages list, where they added the 6 managed metadata columns + the Created, Modified, Createdby and Modifiedby fields.

3. Currently the wiki pages library inside the enterprise wiki has 3,200++ wiki pages.

And the customer is approaching this as follow; that when the wiki pages library reaches 4500 they are going to expand the list threshold to 6,000. and they feel comfortable with this.

So i think if we migrate the above enterprise wiki site collection to SharePoint online, we will be facing many risks, as follow:-

1. if the enterprise wiki reaches 5,000 wiki pages , then the managed metadata will stop working.

2. and even we can not define indexing on any of the manged metadata columns, to force each of the list views to show less than 5,000.

3. So all the enterprise wiki's list views will break in this case.

So can anyone adivce , on what are Microsoft plans for the list threshold? are they planning to expand this?

Second question.. If we chose to migrate the above enterprise wiki site collection into sharepoint online, then what are the approaches that we can follow to allow the metadata navigation to work in-case the wiki pages library exceeds the threshold?