Bruvac: Specifying Mill
Yes, there's a planned errata to introduce the “mill” keyword to earlier cards.
You can already see it in eleven mill cards reprinted in Jumpstart. For example Thought Scour's Jumpstart print says “Target player mills two cards”; it used to say “Target player puts the top two cards of their library into their graveyard”. Tome Scour uses the same template as Thought Scour except it says “five” instead of “two”, so it will assuredly receive errata to say “Target player mills five cards.”
Eli Shiffrin, the rules manager, tweeted guidelines about what to expect with the new mill errata and says it should arrive in Gatherer on Tuesday (meaning the 23rd of June):

Handy rule of thumb on the upcoming &quot;mill&quot; errata (in Gatherer Tuesday): If you look at the cards and then move those specific cards to the yard, it's not &quot;mill.&quot; If you move cards and then look at them (or don't look at them at all), it's probably &quot;mill.&quot; #WotCStaff

He confirms as an example that Mind Funeral will not say “mill” but Traumatize will. This makes it fairly clear Tunnel Vision will not receive errata to say “mill”.