This is an interesting question that I've thought about quite a lot. Especially in regard to the ubiquitous 'RPG elements' we see as a feature of games now. My position is something like this:
If you go back to early classic and traditional RPGs, and trace the evolution of the genre, there's really not one single defining element which is the 'RPG' element. Instead RPGs really evolved as a set of interrelated systems which for a long time were all very much part and parcel with one another. Those systems, however, are not mutually inclusive, and over time - especially over the last generation or so of games - we've seen an unpacking of those various elements, going in both directions: RPGs which exclude or replace certain of the typical systems as not a part of their whole, and other games which season themselves with one or two of these elements integrated with their whole of very different systems.
So the phrase 'RPG elements' seems very apposite to me, as I don't think it's a genre defined by a single aspect, but rather it's a bunch of discrete aspects whcih can be mixed and matched with elements from anywhere else in gaming.
On top of that, there's a distinction to be drawn between a game with 'roleplaying elements': a game with elements of playing a role - and 'RPG elements': genre tropes which are frequently mechanical in nature.
Now, the IE games are pretty traditional and ancestral to the genre, so they all feature a fairly classic and all-encompassing conjunction of RPG elements, and include few elements from elsewhere. That said, Icewind Dale skews hack-and-slash heavy, and has the fewest roleplaying (playing-of-role) systems, whilst Torment is heavy on the roleplaying and is light on a few of the archetypal mechanical elements (combat is underdeveloped and there's no character customisation, picking of feats and skills and suchlike).
So I view the RPG genre as being somewhat modular in nature - whilst we typically see genres as a classification system, and thus all about delineating characteristics, I don't think the RPG genre works this way. It's more like a collection of interrelated systems/tropes/elements which can be mix and matched with other elements from outside itself - in configurations which are predominately RPG, or which are a seasoning over a game of a different nature, and in balances which are purely mechanic to purely playing-of-role.
Defining something as an RPG, then, ends up being pretty contextual. It depends what the specific topic of discussion is, and if the game in question holds those specific RPG elements which bear relation to that topic. The same game may bring a lot to one discussion of RPGs and be irrelevant elsewhere.
For me personally, true roleplaying is about shaping a character. Sculpting a specific identity and pursuing that identity through the world. So, for example, the Walking Dead is an RPG for me in that sense - It's a game that affords me an experience of playing a role. But its mechanical identity is far more heavily descended from point-and-click adventure games. So in a discussion of point-and-click games, I'd bring it up. In a discussion of playing-a-role in games, I'd bring it up. But in an RPG discussion focussed on level ups and combat systems, no, of course it wouldn't fit the active definition, and wouldn't make sense to bring it up, regardless of it personally being an 'RPG' to me for what it fulfils.
Now, as a heritor of the IE games and based on everything we've seen so far, I'd say PE undoubtedly will feature a very large swathe of the classic RPG elements, and it'll be hitting up both the aspects of mechanical and playing-of-role identity, so defining it as an RPG should be pretty uncontroversial and universally applicable anyway.
Did that make any sense?