If Jesus were alluding to a future fulfillment of Matt 5:5 [which is doubtful since the context does not warrant such a conclusion] then doubtless He would have in mind the Jews as natural descendants of David, and the "earth" would be the "land" of Judah which is the subject of Jesus' original source material. [Ps 37:11]
However such a view is not necessarily valid, because I find that the context as a whole denies this. Remember that Vs 5 of Matt 5 is not a text that stands in isolation, but is part of a greater teaching of Jesus, imbedded in a larger section that takes in vss 3-11 All these verses begin with the Greek "markarios" which is best translated as "blessed" [although "happy" is not necessarily wrong. It is just that it conveys a jocularity that is not portrayed by the spiritual depth of the Greek original]
If vs 5 only has a future validation, then those who are "conscious of their spiritual need" can look for no spiritual sustenance today.
The two tier idiocy that is part of WTS "Christianity" is exposed when you realize that only one group can possibly be in view. Those to whom the Kingdom belongs [vss 3, 10] will: see God [vs8] Be called His sons [vs 9] Are the ones who will inherit the earth [vs 5] are the ones who will be comforted [vs 4] be shown mercy [vs 7] will enjoy the fruits of righteousness [vs 6]
Clearly as Nark and the others have shown above, the WTS is aware of this dilemma. Obviously, only one group IS in view. Because of the embarrasing implication of being the "Sons of God" [vs 9] the WTS has to restrict the application of these "Beatitudes" to the "anointed" most of whom being doddering old decrepits these verses are unintelligible. Evidently because of this, these verses which form a basic framework of "Christian Citizenship" and which are much loved by even the most unlearned of true Christians, have never been commented on in context by the WTS. As Nark has shown, it was some 45 years ago that such a comment was attempted.
Christians today recognize themselves as the "disciples" mentioned in vs 1 [although this does not discount a possible application to natural Jews in some restricted context] They are the ones who must portray themselves as Jesus dictates. To be gentle. Merciful. Pure in heart. Be peacemakers. These are the badges we exhibit to the world, and which stamp us as being the stuff of those who can truly be called the sons of God.
It therefore becomes unnecessary to look upon certain verses within the greater context as having some sort of superficial prophetic significance. In other words, it really doe'nt matter what "inherit the earth" means if you do not consciously portray yourself as a son of God