OED publishes a description of its criteria for inclusion:
How does a word qualify for inclusion in the OED?
The OED requires several independent examples of the word being used, and also evidence that the word has been in use for a reasonable amount of time. The exact time-span and number of examples may vary: for instance, one word may be included on the evidence of only a few examples, spread out over a long period of time, while another may gather momentum very quickly, resulting in a wide range of evidence in a shorter space of time. We also look for the word to reach a level of general currency where it is unselfconsciously used with the expectation of being understood: that is, we look for examples of uses of a word that are not immediately followed by an explanation of its meaning for the benefit of the reader. We have a large range of words under constant review, and as items are assessed for inclusion in the dictionary, words which have not yet accumulated enough evidence are kept on file, so that we can refer back to them if further evidence comes to light.
Collins has a slightly different approach to its criteria, but there is a relevant portion, which indicates similar criteria to Oxford:
The editors look at large balanced, representative databases of English to establish how frequently a particular word occurs in the language. Words that do not occur in these databases, or only occur with a minuscule frequency, are not likely to be included in the dictionary.
The editors consider whether words are likely to be encountered in mainstream English or if they are restricted to a particular set of users. Words which are not restricted to a small set of users are more likely to be included in the dictionary.
The editors consider whether words have been used only for a limited period of time, or whether there is evidence for them continuing to be used over a sustained period.
I can't really see that text-speak neologisms like DNTEXT which have limited use are likely to satisfy either set of criteria for some considerable time, if at all. OED3 does include WTF (1985) under W, and LOL (1989) in its own entry, but these have been around for thirty years and have a wider application than your examples.
OED doesn't [yet] include GR8T, but that might become common enough in due course. One issue is that dictionaries tend to rely on printed evidence of usage to cite, and text-speak words appear more rarely in print than their general use might suggest.