al-Hafidh Ibn Rajab al-Hanbali رحمه الله said,
"The apparent outward meaning of the texts shows that whoever turns to Allaah سبحانه و تعالى wholly sincerely, and the conditions of tawbah are all fulfilled in him, then one can assert that Allaah سبحانه و تعالى will accept his tawbah just as one can assert the acceptability of the Islaam of the kaafir when he submits authentically in Islaam. This is the position of the great majority and Ibn 'Abdul Barr's رحمه الله words indicate that it is the consensus.
Some people say that one cannot assert the acceptance of tawbah, but rather that it is hoped for and the person who makes tawbah is subject to the will [of Allaah سبحانه و تعالى]. They sought to prove that by the words of Allaah سبحانه و تعالى:
'Allaah does not forgive anything being associated with Him but He forgives whomever He wills for anything lesser than that,' (4:47) and so He placed all wrong actions subject to His will. They also sought to prove that by the like of His words, Exalted is He:
'O you who have believed, repent to Allaah with sincere repentance. Perhaps your Lord will remove from you your misdeeds and admit you into gardens beneath which rivers flow...' (66:8) and His words:
'But as for those who make tawbah and act rightly, they will hopefully be successful.' (28:67) and His words:
'And turn to Allah in repentance, all of you, O believers, so that hopefully you will have success.' (24:31) and His words:
'And (there are) others who have acknowledged their sins, they have mixed a deed that was righteous with another that was evil. Perhaps Allaah will turn unto them in forgiveness. Surely, Allaah is Oft-Forgiving, Most Merciful.' (9:102)
The apparent outward meaning of this is that it is with respect to the one who turns in tawbah because acknowledgement requires regret. There is in the hadeeth of Ummul Mu'mineen Sayyidah 'Aa'isha as-Siddeeqa bint as-Siddeeq رضي الله عنهما that the Prophet صلى الله عليه وسلم said, 'When the slave acknowledges his wrong action and then turns in tawbah, Allaah سبحانه و تعالى turns to him.' 
The authentic and right position is that of the larger group.
These aayaat do not disprove asserting [that tawbah is accepted], because when the Generous makes one desire and long for something He does not sever one's hopes from that which is desired. For this reason, Sayyiduna Ibn 'Abbaas رضي الله عنهما said, 'The word 'asaa (perhaps, hopefully) from Allaah سبحانه و تعالى is obligatory.'  'Ali Ibn Talhah رحمه الله transmitted it from him.
The reward for eemaan and right action has also been mentioned with the word 'hopefully', but that does not show that it is not something that can be asserted, such as in His word:
'The mosques of Allaah are only to be maintained by those who believe in Allah and the Last Day and establish prayer
As for in His words: '...He forgives whomever He wills for anything lesser than that,' (4:47) then the one who turns in tawbah is one of those whom He wills to forgive, as He informed us in many places in His Book." 
 al-Bukhari, Muslim and others
 at-Tabari, 1655
 Jami' al-'Uloom wal-Himam (Compendium of Knowledge and Wisdom)