Deliberate skipping Salah is a major sin but does not mean disbelieving in Islam (Kufr) as far as the person believes that Salah is obligatory.
Those who deny Salah and don't believe that it is obligatory are considered as disbeliever.
Some Muslim sects like Wahabis claim that skipping Salah makes the person a Kafir right away.
Procrastination and laziness can be a sinful act if it harms the rights of others or causes them any damage whether financial or social or personal etc.
Procrastination and laziness are from the bad habits of the hypocrites (Munafiqs). Quran mentions about Munafiqs: When they stand for Salah (Prayer), they stand with laziness.(Sura 4, Verse 142). There is also an attack in Quran on groups who claimed to be Muslims but were going against the orders of the Prophet. They were mentioned that they don't come for Salah but with laziness. (Sura 9, Verse 54).
In Quran there are many verses blaming those Muslims who used to procrastinate when orders of Allah come e.g. (O you who believe! What is the matter with you, that when you are asked to March forth in the Cause of Allah, you cling to the earth? Did you opt for this worldly life leaving Hereafter? Surely the enjoyment of this worldly life is very little compared with the Hereafter.) Sura 9, Verse 38.
There are many Hadeeths against procrastination and laziness e.g.
1. From Ameerul Mo'mineen that he has written to one of his companions: So, hurry up to utilize what has remained from your life and don't say tomorrow and day after, surely those who were perished before you because of their long hopes and procrastination till the order of Allah (death) came to them suddenly while they were unaware. Biharul Anwar; V.73, P.75.
2. From Imam Muhammad Al-Baqir (AS): Beware from procrastination and postponing, surely it a sea in which many people are destroyed. Biharul Anwar; V.73, P.365.