It's still the present continuous tense. It is usually clear from the context whether we are talking about an action currently in progress or one that will occur in the future.
This usage is preferred over the future tense (जूलिया, तुम कब आओगी? - Julia, when will you come? ) when you know for certain that the event will occur. So, even though you are talking about the future, the sentence has some amount of 'truth' in the present.
So do we call रही a continuous tense marker, and call the other present tense we are learning "simple present"? Can you explain how it corresponds to English simple present and how it does not? I have the impression Indian English speakers use the continuous where and American like me would prefer simple pressent, for example to indicate habitual or repeated actions. I may be mistaken, but I think i have heard sentences such as "I am going every day to work," where I would say "I go to work every day." "I am going" means to me either right now (in process) or begining at some time in the future. Forgive me for belaboring the question, and I may be oversimplifying.
The present-tense forms of the verb होना-'to be' (ie, है,हैं, हूँ, हो) are used as present-tense markers for other verbs. Similarly, the verb रहना (to stay) marks the continuous aspect (for past, present and future tenses).
मैं खता हूँ - I eat - Simple present
मैं खा रहा हूँ - I am eating - Present continuous
मैं खा रहा था - I was eating - Past continuous [था is the past tense form of होना which marks the past tense for all tenses except the simple past]
In most cases, the simple present and the present continuous tenses correspond pretty well with their counterparts in English. Habitual and repeated actions are indicated with the simple present tense in Hindi as well.
The confusion arises mostly in the case of stative verbs and this is likely why some Indians overuse the continuous aspect. For stative verbs (like 'know', 'understand', 'hear' etc), English does away with the present continuous and uses the simple present instead. However, Hindi does not consider many of these verbs as stative or uses nouns/adjectives in their place. So, Indian ESL speakers are often confused as to why these verbs cannot be used with the continuous aspect leading to sentences like 'I am knowing her' or 'I am understanding'. Note that, while common, this usage is considered wrong in Indian English as well.
Another instance of present continuous overuse that is much more tolerated in Indian English is related to the present perfect continuous tense (have/has been ---ing). Hindi also has a corresponding tense but since it is considered formal (and perhaps a little pretentious), the present continuous often takes its place. So, you see sentences like 'I am waiting since one o'clock' translated literally from 'मैं एक बजे से इंतज़ार कर रहा हूँ' .
Thank you Vinay2 for this conversation. I see that the the sentence I quoted as an example probably came from my hearing the present continuous used in place of the present perfect. I have probably heard sentences such as "I am going to work every day since (or for?) four years." That perfect/present distinction is a problem for many ESL speakers.