This is a common prooftext for Old Testament trinitarianism. I think we need to consider certain reasons to affirm the traditional understanding.
1. The creational context leads us to suppose that it is God that is in mind. God created alone and it seems that he would’ve created man alone. The passage is polemical to the other ANE gods to show God is the true God. The focus seems to be on the superiority of God rather than God and his divine friends:
2. Angels or other divine beings haven’t been introduced into the narrative. It seems a bit abrupt to mention them here.
Gen 1 is notably silent on the creation of angels. So Gen 1 hasn’t laid a foundation for that referent. It would be very abrupt to assume an allusion to the heavenly court when Gen 1 hasn’t even said anything about the existence or origin of angels.
In fairness, one might defend the angelical interpretation by noting that the context of Gen 1 includes the entire Pentateuch. Certainly the Pentateuch mentions angels. Indeed, there are several references to angels in Genesis alone.
On the other hand, there’s nothing in the Pentateuch that clearly refers to the angelical heavenly court. Those all occur outside the Pentateuch. Perhaps the closest we come to it is “Jacob’s ladder.”
Since, moreover, Gen 1 is a creation account, if angels are the point of reference for God’s plural address, I think we’d still expect the creation of angels to be mentioned. Gen 1 does explain some things in reference to other things, but it does so by building on earlier fiats. God is said to make one thing at an earlier stage, and that, in turn, is a point of reference for a later development.
In Gen 1, there are arguably two divine agents in play: God and God’s Spirit. In Scripture, “spirits” are personal agents, and the “Spirit of God” is a divine agent. So, in context, it would make sense if this is a dialogue between God and God’s Spirit. This isn’t fully Trinitarian, but it’s a first step in that direction.
We also have some other trinitarian evidence from Gen 19:
3. It also seems unlikely to be a plural of majesty:
Many interpreters in the past regarded the plural as a plural of majesty (pluralis majestatis). This means that God speaks of himself and with himself in the plural number. This suggestion, held by only a few today, needs some consideration. Plurals of majesty exist with nouns in the Hebrew language2s but there are no certain examples of plurals of majesty with either verbs or pronouns. The only possible exception where there may be a plural of majesty with a pronoun is said to come from post-exilic times. A statement by a Persian king quoted in En 4:1829 reads, “The document which you sent to us has been translated and read before me” ( NAS ). It had been suggested, however, that more probably the “us” means “my government” or “my court,” and the pronoun “me” equals “me personally,” so that “in fact ‘us’ is here not really a plural of majesty.'”O If this suggestion is correct, then the OT nowhere contains a verb or pronoun used in connection with a plural of majesty. Even if there were an exception, it is correct that the verb used in Gn 1:26(עָשָׂה ʿâsâh) is never used with a plural of majesty.31 There is no linguistic or grammatical basis upon which the “us” can be considered to be a plural of majesty. It is for this reason that this interpretation is today generally abandoned.