The Greek expression for "present truth" is: te paroúse aletheía, which can be translated literally as: the being beside truth; the being present truth; the present truth.
The second word in the Gr. expression paroúse is related to parousía which we being taught in the KH that it means "presence." Both paroúse and parousía are related to páreimi which basically means, (from pará, beside and eimí, be). Various versions below can help us understand the expression:
ISV: Therefore, I intend to keep on reminding you about these things, even though you already know them and are firmly established in the truth that you now have.
Darby: Wherefore I will be careful to put you always in mind of these things, although knowing them and established in the present truth.
Weymouth: For this reason I shall always persist in reminding you of these things, although you know them and are stedfast believers in truth which you already possess.
Young's: Wherefore, I will not be careless always to remind you concerning these things, though, having known them, and having been established in the present truth,
NSB: I will always be ready to remind you of these things. Even though you know them, and are established in the truth that is present with you.
21st Cent: "...in the truth as presently revealed."
Twentieth Cent: "...in the Truth that you now hold."
Vincent's Word Studies: In the present truth (ε?ν τη?? παρου´ση? α?ληθει´α?)
i.e., the truth which is present with you through the instruction of your teachers; not the truth at present under consideration. See on 2 Peter 1:9; and compare the same phrase in Colossians 1:6, rendered, is come unto you.
Barnes' Notes: And be established in the present truth - That is, the truth which is with you, or which you have received - Robinson's Lexicon on the word πα´ρειμι pareimi. The apostle did not doubt that they were now confirmed in the truth as far as it had been made known to them, but he felt that amidst their trials, and especially as they were liable to be drawn away by false teachers, there was need of reminding them of the grounds on which the truths which they had embraced rested, and of adding his own testimony to confirm their Divine origin. Though we may be very firm in our belief of the truth, yet there is a propriety that the grounds of our faith should be stated to us frequently, that they may be always in our remembrance. The mere fact that at present we are firm in the belief of the truth, is no certain evidence that we shall always continue to be; nor because we are thus firm should we deem it improper for our religious teachers to state the grounds on which our faith rests, or to guard us against the arts of those who would attempt to subvert our faith.